what damage could a toyota corolla 2006 have if it has sat and not been started for 3 years

First off I would drain the fuel do not try to start it with the old fuel as it could damage the fuel system if you do. Also I would change all fluids and have the tires and battery inspected. Good Luck

Sure it can be brought back to life. I agree with Michael. Do not attempt to start car --yet. Do NOT drive on those tires. Definitely new battery. I don't know about ALL fluids, like power steering and brake fluid, even coolant should be ok But ALL needs to be checked. Absolutely yes on oil change, use 5W30 synthetic and a quality filter. BEFORE starting it. IF it was near empty on gas when parked, there is very likely water from condensation ... yup even in the sealed system. And after draining tank, which you can do by taking our back seat and use a gasoline approved pump with hoses on a power drill from the fuel pump access - you do not have to drop the tank, then use an alcohol-base additive with fresh gas.. Bottom line... yes it can be brought back to full, normal function. BTW do you want to sell it? I am interested------

Pull the engine cover off and after you put fresh gas in stick a paper clip or small screwdriver in the schrader valve on the fuel rail, it's a 1.8L - 1ZZ FE and looks just like a tire stem. Turn key to run without starting and allow fuel to squirt out. It will go everywhere, but no worries. Just allow it to evaporate before starting car.

Good info Jim, I didn't think of that. But oh so true.